Need help with rims and tires...

[JasonNagra]

Okay I recently just got my 91 240 Fast back and I love the car. I have been reading this site along with other 240 forums for about a year now. I did a search and couldn't really find anything. I just lowered my car with Eibach sportlines and KYB AGX shocks. (I love the combo by the way, the drop is perfect and handling is excellent). I want to get some plain 5 star 16" wheels to make the car look a little better. What size tire (i was thinking 225/50/16 all around) can I go with without affecting the speedo or any sort of steering geometry? And also what offset of wheel do I need?? I know the bolt pattern is 4x114.3, but the with the rest I am a little clueless. Thank you everyone.

[Jeff240sx]

I'm not going to do your math for ya, but your car's spedo is measured by revolutions of the wheel.  If you enlarge your wheel diameter, geometry and pi*d means you will go further between revolutions and hence faster than your spedo measures.
If you go from 15" rims to 16" rims, you have to cut off 1" of tire height.  Stock on a SE model is 16" with 205/50/r16... so 225/50 are going to be 10mm higher than stock... so you'd have to go with 225/45 to make it even again... just do math, and you'll be fine.
And yes, they will all fit.
-Jeff

[JasonNagra]

Okay so I will go with the 225/45/16's all around, but what about offset? Is there a certain offset that I need to keep everything in check? I think its like 7.5 or 7 for 16" wheels but I'm really not sure. Also do you think 225 tires are the best size to run on the S13 with 16" rims?? Thank you again.

Also, i know the 7.5 following the 16 in: 16 x 7.5 means the offset but what does it mean when people are like +32??

[adey]

Nup! you got the last two numbers mixed up. a 16" wheel with 7.5" offset would be fucking retarded... haha...
16x7.5 +32  is a 16" diametered wheel that's 7.5" wide, and has a 16mm offset. Look at http://www.tirerack.com for more info on offset etc.

[orange-grey]

225/50's will be slightly taller than stock while 225/45's will be slightly shorter. Neither will affect your speedo too much, but obviously the 45's will give you slightly better gearing, slightly less rotational weight, and shorter stiffer sidewalls.

I think you're confusing wheel width and offset. 7" and 7.5" are wheel widths. +40mm is an example of an offset, in this case the stock offset, which is the difference between the wheel centerline and the mounting face. Too much offset and your wheels tuck inwards and will probably hit all sorts of stuff. Too little offset and the wheels will stick out like a lowrider. Ideally you want to stick as close at possible to stock, but you can go a tad less in order to fit wider wheels. The only real way to find out is to measure your current clearance and do some math. I'm going to take a wild guess and say for a 7.5" wheel you're gonna want around a +33 offset, but don't hold me to that.  

And 225's are great, not only because thats the biggest you can practically go in front, but it's also the max width allowed in Solo2 STS class if you ever decide to attend an autocross. Which really should be mandatory for every 240 enthusiest. &nbsp;<img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/thumbs-up.gif" border="0" valign="absmiddle" alt=':thumbsup:'>

[Jeff240sx]

Are you running 16" stock wheels? Because if not, and you don't have a SE model, which I really don't assume you do because you mention 4-lug, you have 15" rims. Not only will you be adding an inch to the rim, but you will add more tire too.
Either you should swap instrument panels or go with low profile tires (225/40 or 225/35). There is a tire calculator Here (http://www.miata.net/garage/tirecalc.html)
This will clear up most problems. Input stock tire size, and new tire size, and it will tell you how far off the spedometer will read in both a percentage and deviation at 60mph.
Have fun, and play around!
-Jeff

[JasonNagra]

I don't have the SE model and I do have the 4 lug. So then the width, meaning the measurement of 7 or 7.5 really has nothing to do with anything?? How does that play a role or how is that width significant? Which width do i need for the 225 tires I want to use?? Ok so the offset of the rim that I will need will approximatley be 33?? Also can you guys give me some examples of 5 star wheels in 16" that will fit my application?? I like the borbet type B's. Im looking for cheap-er lighter type wheels... Thank you everyone for all of your help.

[Jeff240sx]

The rim width dictates the tire size you have to use. &nbsp;I am pretty sure stock SE rims are 6.5" and the largest tire that you would want to run on them would be 215mm. &nbsp;So you'd probably have to go with 7" rims... or possibly 7.5", but then you might need even wider tires. &nbsp;Stock offset, like was mentioned before is +40mm from center, and you want to stay as close to that as possible. &nbsp;33mm is kinda a large offset. &nbsp;There is a lot of math involved with spending $1500+ on some rims and tires. &nbsp;Be sure to do it, or you'll kick yourself for a long time to come
-Jeff

[240 2NR]

For a 225 series tire, I'd recomend trying to get a 7.5" rim. I have 16x7's running 225/45/16 tires and they bulge a bit. Whenever I look at them I wish I had gotten a 7.5" rim, but then I remember that my wheels only cost $500 shipped and I'm happy again. When I get a new set next summer, I'm thinking it will be 17x8.

Oh, and the stock tire size for an S13 is 195/60/15 for most cars, and the handling package (super hicas) cars came with 205/60/15. &nbsp;As far as I know all wheels came in a +40 offset, and a 4x114.3 bolt pattern. &nbsp;S14's with the 5 point wheels were 16x6.5 +40 with a 5x114.3 bolt pattern, wearing 205/55/16 (iirc). &nbsp;Base model S14's came with 4 lug wheels, though I'm not sure what size.

Helpful links:
Tire Size Calculator (http://www.miata.net/garage/tirecalc.html) use this as a guide, but check published specs from the manufacterer before buying as these size are close (example, Kuhmos run a bit tall in my experience)

Offset (http://www.tirerack.com/wheels/tech/offset.htm)

Plus Sizing (http://www.tirerack.com/wheels/tech/plusone.htm)

[JasonNagra]

Okay, now I have a grasp on all this, thank you everyone again for all your help.